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                  <p class="p_Heading1"><span class="f_Heading1">Fork</span></p>



  
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<td valign="top" width="202" style="width:202px;"><p class="p_TextIndentedL2"><img src="d_forkjoinacross.png" width="85" height="66" border="0" alt="d_ForkJoinAcross"></p>
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<td valign="top" width="172" style="width:172px;"><p class="p_TextIndentedL2"><img src="d_forkjoinup.png" width="85" height="82" border="0" alt="d_ForkJoinUp"></p>
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<p class="p_TextIndentedL2"><img src="activity%20-%20forkjoin2.png" width="367" height="118" border="0" alt="Activity - ForkJoin2"></p>
<p class="p_BodyText"><span class="f_BodyText">See</span><span class="f_BodyText" style="font-style: italic;"> UML Superstructure Specification, v2.1.1, figure 12.95 p. 377</span><span class="f_BodyText">.</span></p>
<p class="p_BodyText"><span class="f_BodyText">These elements are used in both <a href="activitydiagram.htm">Activity</a> and <a href="statediagram.htm">State Machine</a> diagrams. With respect to State Machine diagrams, a </span><span class="f_BodyText" style="font-style: italic;">Fork</span><span class="f_BodyText"> <a href="pseudo_states.htm">pseudo-state</a> signifies that its incoming transition comes from a single state, and it has multiple outgoing transitions. These transitions must occur concurrently, requiring the use of concurrent <a href="region.htm">regions</a>, as depicted below in the <a href="compositestate.htm">Composite State</a>. Unlike </span><span class="f_BodyText" style="font-style: italic;"><a href="choice.htm">Choice</a></span><span class="f_BodyText"> or </span><span class="f_BodyText" style="font-style: italic;"><a href="junction.htm">Junction</a></span><span class="f_BodyText"> pseudo-states, Forks must not have triggers or guards. The following diagram demonstrates a Fork pseudo-state dividing into two concurrent regions, which then return to the </span><span class="f_BodyText" style="font-style: italic;">End State</span><span class="f_BodyText"> via the</span><span class="f_BodyText" style="font-style: italic;"> <a href="join.htm">Join</a></span><span class="f_BodyText"> pseudo-state.</span></p>
<p class="p_TextIndentedL2"><img src="state%20--%20join.png" width="710" height="324" border="0" alt="State -- Join"></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">OMG UML Specification</span></p>
<p class="p_BodyText"><span class="f_BodyText">The OMG UML specification (</span><span class="f_BodyText" style="font-style: italic;">UML Superstructure Specification, v2.1.1, p. 538</span><span class="f_BodyText">) states:</span></p>
<p class="p_OMGText"><span class="f_OMGText">Fork vertices serve to split an incoming transition into two or more transitions terminating on orthogonal target vertices (i.e. vertices in different regions of a composite state). The segments outgoing from a fork vertex must not have guards or triggers.</span></p>




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